The present invention relates to an apparatus for assisting steering when a vehicle is moving backward. More specifically, the present invention relates to a steering assist apparatus that includes a camera for capturing the view from the rear and a monitor for displaying the captured view along with marking for assisting the driver.
In the prior art, apparatuses for showing the view from the rear of a vehicle have been proposed. Such an apparatus allows the driver to see the view from the vehicle rear without actually turning around. Japanese Examined Patent Publication No. 2-36417 discloses a rear monitoring apparatus, which includes a video camera for capturing view from the rear of the vehicle, a video monitor for showing the captured view and a sensor for outputting signals representing the angle of vehicle wheels. The apparatus generates marker signals based on signals from the wheel angle sensor and superimposes a marker on the video monitor. The positions of the markers on the monitor correspond to the direction in which the vehicle is being backed. The direction is determined in accordance with the steered angle of the vehicle wheels. The apparatus includes a read only memory (ROM), which stores steered angle data of the vehicle wheels and marker position data. When the vehicle is moving backward, the course of the vehicle is predicted based on the steered angle data. The predicted course is displayed by rows of the markers superimposed on the monitor screen showing the image captured by the video camera.
Japanese Unexamined Patent Publication No. 10-175482 discloses an apparatus for assisting the view from the rear of a vehicle. This apparatus includes a detector for detecting the angle of the front wheels, a vehicle speed sensor, a camera for capturing the view from the rear of the vehicle and monitor for displaying the view. The apparatus also includes a computer. When the vehicle is moving backward, the computer computes the path of the rear wheels based on the steered angle of the front wheels. The predicted path is converted into path image data, which represents the predicted path as viewed from the rear camera. The path image data is further converted into linear marking data, which corresponds to the monitor screen. The linear marking data is superimposed on the image of the view from the vehicle rear shown on the monitor screen.
Japanese Unexamined Patent Publication No. 10-244891 discloses a parking assist apparatus. This apparatus includes first and second image pickup means provided at the sides of the vehicle to capture the image of the vehicle surroundings. The apparatus superimposes lines on the image captured by the image pickup means. The lines permit the driver to judge whether parallel parking is possible.
The apparatuses of the publications No. 2-36417 and No. 10-175482 both show the rear view captured by a camera and predict the path of the vehicle or the path of the rear wheels based on the current wheel angle. The apparatuses then superimpose the predicted path on the monitor screen. The superimposed path does not correspond to the vehicle length or the wheelbase. When passing another car in a winding road such as a mountain road, the driver may have to move his vehicle backward until the vehicle reaches a spot that is wide enough for two vehicles to pass each other. At this time, the apparatuses of the publications No. 2-36417 and No. 10-175482 will show the view from the rear and the predicted path on a monitor. Accordingly, the driver will know whether maintaining the angle of the front wheels will cause the vehicle to leave the road.
However, as shown in FIG. 26, all the currently predicted data of a path 41 representing the vehicle path or the predicted rear wheel path is shown on a monitor screen 42. Thus, if the curvature of the road 43 is not constant for a relatively long distance and the wheel angle does not correspond to the curvature of the road 43, the upper end of the superimposed path 41 does not match the road 43 on the screen 42. Generally, the curvature of a road is not constant for a long distance on winding roads such as mountain roads. Therefore, the superimposed path 41 is often partly off of the a road on the screen 42, which at least permits the driver to realize that maintaining the current wheel angle will cause the vehicle to leave the road. However, the superimposed path 41 does not give the driver information necessary for judging how he should manipulate the steering wheel. In other words, the superimposed path 41 cannot be used for determining the steering amount of the steering wheel.
When parallel parking a vehicle, the driver has to switch the direction of steering. However, the superimposed path 41 does not help the driver to judge when to switch the steering direction.
The apparatus of the publication No. 10-244891 assists the driver when parking a vehicle. The apparatus needs two image pickup means to capture front and rear images from the vehicle side. The apparatus shows a line for indicating whether parallel parking is possible. The computation of the line is complicated.